1. Field of the Invention
The present invention relates to a display device, and more particularly to a technique which is effectively applicable to a display device which includes a direct backlight unit.
2. Description of Related Art
Conventionally, as a display device, there has been known a device which displays an image or a video using light from a light source such as a liquid crystal display device, for example. In the liquid crystal display device, on a back side of a liquid crystal panel which fills a liquid crystal material between a TFT panel on which TFT elements are arranged in an array and a counter substrate, a light source (a backlight unit) is mounted.
The backlight unit is a unit (a member) which radiates light to a whole surface of the liquid crystal panel after converting light from a linear light source such as a cold cathode fluorescent tube or the like, for example, into a planar light, wherein the backlight unit is classified into a direct backlight unit and an edge-light backlight unit.
In the direct backlight unit, for example, the fluorescent tube is arranged right below the liquid crystal panel. In such a backlight unit, for example, a reflector is arranged in the inside of a box-like housing (a frame), and one or a plurality of fluorescent tubes are arranged above the reflector. Further, above the fluorescent tube, an optical sheet and a light diffusion plate are arranged.
The direct backlight unit is, in general, used in a liquid crystal display device or the like which is required to exhibit high luminance. For example, the direct backlight unit is used as a light source of a display device such as a liquid crystal display for a PC (a personal computer), a liquid crystal television receiver set or the like.
Further, with respect to the liquid crystal display or the liquid crystal television receiver set, recently, the large sizing of the display panel is in progress and hence, the light diffusion plate which is mounted on the backlight unit becomes also large-sized. Accordingly, when the light diffusion plate is supported on the housing in a state that end portions of the light diffusion plate are brought into contact with the housing, the light diffusion plate is deflected and hence, a uniformity ratio of luminance is lowered. Accordingly, recently, for example, there has been proposed a backlight unit in which a support member is arranged in the inside of the housing and the light diffusion plate is supported on the support member thus preventing the deflection of the light diffusion plate and enhancing the uniformity ratio of luminance (for example, see Japanese Patent Laid-open Hei7(1995)-64084).
In the backlight (illumination device) which is described in the above-mentioned document, on an inner bottom surface of a reflector which corresponds to the above-mentioned housing, a transparent support member which supports an optical member such as a light control sheet (a diffusion plate) or the like on an inner surface of the sheet is mounted in an elected manner.